1. Field of the Invention
The present invention relates to a method of manufacturing thin-film transistors using nanoparticles and thin-film transistors manufactured by the method. More particularly, the present invention relates to top-gate thin-film transistors formed on flexible substrates using nanoparticles and a method of manufacturing the same, in which hydrophilic buffer layers are deposited on the substrates to facilitate formation of nanoparticle films, and sintered nanoparticles are used as channel layers of the thin-film transistors and dielectric materials of high dielectric constant are also used as gate layers to form top gate electrodes on the gate dielectric layers, thereby enabling low-voltage operation and low-temperature fabrication.
2. Description of the Related Art
In general, field-effect thin-film transistors currently used in flat panel display including a liquid crystal display (LCD) are manufactured by using amorphous silicon (a-Si:H) or polycrystalline silicon as channel layers, and by using silicon oxide or nitride as gate dielectric layers.
In recent years, extensive researches on the manufacture of thin-film transistors using organic materials such as pentacene or hexathiophene have been made in order to enable a low-temperature process and low-cost fabrication. However, such organic thin-film transistors have inherent limitations in view of mobility, physical and chemical stability and the like. Further, there are difficulties in that the organic thin-film transistors are directly applied to processes studied so far for inorganic semiconductors.
In order to overcome such difficulties, B. A. Ridley, B. Nivi, and J. M. Jacobson in MIT fabricated thin-film transistors using CdSe nanoparticles in 1999 (see Science, vol. 286, p. 746).
In the study, a representative transistor with a field effect mobility of about 1 cm2/Vsec and an on/off current ratio of 104 or more has been manufactured to propose a possibility of a thin-film transistor with channels composed of nanoparticles. In 2005, D. V. Talapin and C. B. Murray in IBM also manufactured thin-film transistors with channels composed of PbSe nanoparticles (see Science, vol. 310, p. 86).
In this study, hydrazine was chemically treated on nanoparticle films to improve the conductivity of the films. Further, n- and p-channel transistors were manufactured through the heat treatment. When inorganic semiconductor nanoparticles are employed in this way, an advantage of processes in such a solution state as in an organic thin film transistor can be achieved and basic problems associated with organic materials can also be solved.
However, transistors developed so far using inorganic semiconductor nanoparticles, including most organic thin film transistors, are back-gate transistors which use SiO2, i.e. oxidized silicon substrates, as gate dielectric layers. Thus, a gate voltage of several tens volts or more is required to operate the transistors.